Figure 1

Integrating high-resolution FTIR into a back-projected floor allows the floor to see the pressure distribution of the user's soles (inset top left, as seen from below). In the shown situation, the floor ignores the foot on the right based on its posture, yet allows the foot on the left to interact. By identifying the user based on her sole patterns, the floor has attached a user-specific high-precision pointer to her foot, which allows her to operate tiny controls, here a keyboard.

Abstract

Tabletop applications cannot display more than a few dozen on-screen objects. The reason is their limited size: tables cannot become larger than arm's length without giving up direct touch. We propose creating direct touch surfaces that are orders of magnitude larger. We approach this challenge by integrating high-resolution multi-touch input into a back-projected floor. At the same time, we maintain the purpose and interaction concepts of tabletop computers, namely direct manipulation.

We base our hardware design on frustrated total internal reflection. Its ability to sense per-pixel pressure allows the floor to locate and analyze users' soles. We demonstrate how this allows the floor to recognize foot postures and identify users. These two functions form the basis of our system. They allow the floor to ignore users unless they interact explicitly, identify and track users based on their shoes, enable high-precision interaction, invoke menus, track heads, and allow users to control high-degree of freedom interactions using their feet. While we base our designs on a series of simple user studies, the primary contribution on this paper is in the engineering domain.